Elementary plant Biochemistry and Biotechnology (2+1)

Basic features of RNA synthesis

Thus, a gene, which code the genetic information first transcribed as RNA. The essential chemical characteristics of the synthesis of RNA are following:

1. The precursors in the synthesis of RNA are the four ribonucleoside 5’ –triphosphates (NTP) ATP, GTP, CTP and UTP.
2. In the polymerization reaction a 3’OH group of one nucleotide reacts with the 5’ – triphosphate of a second nucleotide; pyrophosphate is removed and a phosphodiester bond results by the activity of RNA polymerase.
3. The sequence of bases in an RNA molecule is determined by the base sequence of the DNA. Each base added to the growing end of the RNA chain is chosen by its ability to base – pair with the DNA strand used as a template; thus the bases C, T, G and A in a DNA strand cause G, A, C and U, respectively, to appear in the newly synthesized RNA molecule.
4. The DNA molecule being transcribed is double stranded, yet in any particular region only one strand serves as a template.
5. RNA chain grows in the 5’→3’ direction (antiparellel) as that of DNA synthesis.
6. RNA polymerases, in contrast with DNA polymerases, are able to initiate chain growth; that is, no primer is needed.
7. Only ribonucleoside 5’- triphosphates participate in RNA synthesis and the first base to be laid down in the initiation event is a triphosphate (Fig).


The synthesis of RNA consists of four discrete stages

1. Binding of RNA polymerase to a template at a specific site
2. Initiation
3. Chain elongation 4. chain termination and release.